The present invention relates to air conditioning systems. More particularly, this invention relates to measures to control air conditioning capacity.
A conventional multi type air conditioning system in which a plurality of indoor units are connected to a single outdoor unit, such as one disclosed in Japanese Patent Kokai Publication No. H02-230063, has been known.
The indoor unit comprises a first compressor which inverter controls capacity and a second compressor which controls capacity by means of an unload mechanism. And the outdoor unit adjusts the capacity of air conditioning by controlling the capacity of each of the two compressors.
In other words, during cooling mode operations, the capacity of each of the two compressors is controlled such that evaporating temperature becomes a given value, whereas, during heating mode operations, the capacity of each of the two compressors is controlled such that condensing temperature becomes a given value.
On the other hand, the indoor unit adjusts the capacity of cooling by performing control so that the degree of superheating becomes constant, for example during cooling mode operations.
Problems that the Invention Intends to Solve
In the above-described conventional air conditioning system, the air conditioning capacity of the outdoor unit is controlled such that evaporating temperature or condensing temperature maintains a constant value all the time. In other words, in conventional air conditioning systems, the air conditioning capacity of an outdoor unit is controlled so as to maintain a plurality of indoor units in such a state that each indoor unit is able to continuously exhibit a respective specified air conditioning capacity.
In the foregoing air conditioning system, the evaporating temperature or the condensing temperature is held at a fixed value. This means that, even when it is sufficient for an indoor unit to operate at a less air conditioning capacity, the outdoor unit is operated at a great air conditioning capacity.
Therefore, even when the air conditioning load is small during for example an intermediate period, the indoor unit operates at the same air conditioning capacity as when the air conditioning load is at its maximum, thereby resulting in an excess of capacity.
As a result of the above, the frequency at which the indoor unit is repeatedly operated and stopped becomes higher. This produces problems, that is, room temperature varies greatly and the capacity of compressors becomes unstable.
Further, the frequency at which the compressor is repeatedly driven and stopped becomes higher, which causes the drop in durability due to stress produced when the compressor is driven or stopped.
Furthermore, the excess of air conditioning capacity produces problems such as a poor operating efficiency and an uneconomical operation.
Bearing in mind the above-mentioned problems, the present invention was made. Accordingly, an object of the present invention is to suppress air conditioning capacity excess and to reduce both the frequency at which a utilization unit is repeatedly operated and shut down and the frequency at which a compressor is repeatedly driven and shut down.
The present invention is an invention for variably controlling the control target value of a heat source unit.
More specifically, the first invention is directed to an air conditioning system for providing air conditioning, the air conditioning system comprising a refrigerant circuit (15) formed by connection of a heat source unit (11) and a plurality of utilization units (12, 13, . . . ). In this invention, the air conditioning capacity of the heat source unit (11) is controlled such that a physical quantity of refrigerant circulating through the refrigerant circuit (15) becomes a target value, and wherein the target value is altered and set.
Further, the second invention is directed to an air conditioning system for providing air conditioning, the air conditioning system comprising a refrigerant circuit (15) formed by connection of a heat source unit (11) and a plurality of utilization units (12, 13, . . . ). The second invention further comprises a capacity controlling means (91) for controlling the air conditioning capacity of the heat source unit (11) so that a physical quantity of refrigerant becomes a target value, and a target value adjusting means (92) for altering the target value of the capacity controlling means (91).
Further, the third invention is an invention according to the second invention in which the target value adjusting means (92) is configured so as to variably control the target value correspondingly to the air conditioning load characteristics of a building.
Further, the fourth invention is an invention according to the second invention in which the target value adjusting means (92) is configured so as to variably control, according to the control characteristics of the target value and based on the temperature difference between a set temperature of an air conditioning space and an outside temperature, the target value.
Further, the fifth invention is an invention according to the second invention in which the target value adjusting means (92) includes a deciding means (93) for determining the control characteristics of the target value correspondingly to the air conditioning load characteristic a building, and an altering means (94) for variably controlling, according to the target value control characteristics determined by the deciding means (93) and based on the temperature difference between a set temperature of an air conditioning space and an outside temperature, the target value.
Further, the sixth invention is an invention according to any one of the first to fifth inventions in which during cooling mode operations the refrigerant physical quantity is an evaporating pressure.
Further, the seventh invention is an invention according to any one of the first to fifth inventions in which during cooling mode operations the refrigerant physical quantity is an evaporating temperature.
Further, the eighth invention is an invention according to any one of the first to fifth inventions in which during heating mode operations the refrigerant physical quantity is a condensing pressure.
Further, the ninth invention is an invention according to any one of the first to fifth inventions in which during heating mode operations the refrigerant physical quantity is a condensing temperature.
Further, the tenth invention is an invention according to any one of the first to fifth inventions in which the air conditioning capacity of the heat source unit (11) is controlled by controlling the capacity of each compressor (41, 42) of the heat source unit (11).
Further, the eleventh invention is an invention according to either the third invention or the fifth invention in which the building load characteristics are determined based on the amount of internal heat generation of the building and the amount of external heat.
Further, the twelfth invention is an invention according to the fifth invention in which a temperature detecting means (74) for the detection of refrigerant evaporating temperatures during cooling mode operations is provided. And, the capacity controlling means (91), which takes as a refrigerant evaporating temperature a target value during cooling mode operations, is configured to control the air conditioning capacity of the heat source unit (11) so that an evaporating temperature that the temperature detecting means (74) detects becomes the target value. In addition, the deciding means (93) of the target value adjusting means (92) is configured so as to determine the control characteristics of the target value of the evaporating temperature. Furthermore, the altering means (94) of the target value adjusting means (92) is configured so as to variably control the target value of the evaporating temperature.
Further, the thirteenth invention is an invention according to the fifth invention in which a temperature detecting means (76) for the detection of refrigerant condensing temperatures during heating mode operations is provided. And, the capacity controlling means (91), which takes as a refrigerant condensing temperature a target value during heating mode operations, is configured to control the air conditioning capacity of the heat source unit (11) so that a condensing temperature that the temperature detecting means (76) detects becomes the target value. In addition, the deciding means (93) of the target value adjusting means (92) is configured so as to determine the control characteristics of the target value of the condensing temperature. Furthermore, the altering means (94) of the target value adjusting means (92) is configured so as to variably control the target value of the condensing temperature.
Further, the fourteenth invention is an invention according to any one of the fourth, fifth, twelfth, and thirteenth inventions in which the target value adjusting means (92) is configured such that the target value control characteristics are set manually.
Further, the fifteenth invention is an invention according to any one of the fourth, fifth, twelfth, and thirteenth inventions in which the target value adjusting means (92) is configured such that the target value control characteristics are set based on an input signal fed from external setting means (9b) via a communication line (9a).
Further, the sixteenth invention is an invention according to any one of the fourth, fifth, twelfth, and thirteenth inventions in which the target value adjusting means (92) is configured such the target value control characteristics are automatically set by learning according to the state of an operation during air conditioning.
Finally, the seventeenth invention is an invention according to the sixteenth invention in which the deciding means (93) of the target value adjusting means (92) is configured such that the target value control characteristics are set by learning according to the number of times air conditioning operation is brought to a halt.
To sum up, in accordance with the present invention, refrigerant circulates between the heat source unit (11) and the utilization units (12, 13, . . . ) for providing air conditioning. And, during air conditioning operations, the air conditioning capacity of the heat source unit (11) is controlled such that a physical quantity of refrigerant in the refrigerant circuit (15) becomes a target value and the target value is altered and set.
More specifically, for example, during cooling mode operations, the target value adjusting means (92) determines the control characteristics of an evaporating temperature target value, and the evaporating temperature target value or evaporating pressure target value is altered.
Further, during heating mode operations, the target value adjusting means (92) determines the control characteristics of a condensing temperature target value, and the condensing temperature target value or condensing pressure target value is altered.
When such a target value is altered, the capacity controlling means (91) takes a refrigerant evaporating temperature or a refrigerant condensing temperature as a target value and controls the air conditioning capacity of the heat source unit (11) in such a way that either an evaporating temperature that the temperature detecting means (74) detects or a condensing temperature that the temperature detecting means (76) detects becomes a target value. For example, compressor capacity is controlled such that the evaporating temperature or the condensing temperature becomes a target value.
Further, in the deciding means (93) of the target value adjusting means (92), either a target value control characteristic is manually set, a target value control characteristic is set based on an input signal fed from the external setting means (9b) via the communication line (9a), or a target value control characteristic is automatically set by learning according to the state of an operation during air conditioning.
Effects of the Invention
Therefore, in accordance with the present invention, it is arranged such that a refrigerant temperature target value is altered based on an air conditioning load of a building for controlling the air conditioning capacity of the heat source unit (11), thereby making it possible to perform operations at a corresponding air conditioning capacity to the building air conditioning load.
That is, when it is sufficient for the utilization units (12, 13, . . . ) to operate at a less air conditioning capacity, the heat source unit (11) also can be operated at a less air conditioning capacity.
As a result, the utilization units (12, 13, . . . ) can be prevented from being operated at an excessive capacity during for example an intermediate period. Because of this, it is possible to reduce the frequency at which the utilization units (12, 13, . . . ) are repeatedly operated and shut down. And, in addition to making it possible to reduce variation in the temperature of an air conditioning space, compressor capacity can be made stable.
Further, since the frequency at which the compressors (41, 42) are repeatedly driven and shut down is reduced, this reduces stress which is produced when they are driven or shut down, thereby improving the durability of the compressors (41, 42).
Furthermore, since it is possible to suppress an excess of air conditioning capacity, this improves operating efficiency. As a result, COP (Coefficient Of Performance) is improved and improvements in economy can be achieved.
Further, in accordance with either the fourth invention or the fifth invention, the target value is altered depending on the temperature difference between a set temperature and an outside temperature, whereby air conditioning capacity can be increased for example at the beginning of an operation. For example, if the indoor temperature is higher than a set temperature during cooling mode operations, or if the indoor temperature is lower than a set temperature during heating mode operations, this increases the temperature difference between either refrigerant evaporating temperature or refrigerant condensing temperature and indoor suction air temperature, thereby making it possible to provide an increased air conditioning capacity. As a result, it is possible to provide improved comfortability
Further, when there occurs sudden variation in load, the air conditioning capacity can be increased by making a change in the set temperature. This makes it possible to improve comfortability.
Furthermore, when performing air conditioning by introducing outdoor air, the air conditioning capacity will vary depending on the inside/outside temperature difference, thereby further improving comfortability. For example, an air conditioning capacity required to meet a set blow-out temperature is determined by the temperature difference between suction air temperature and set blow-out air temperature. Because of this, it is possible for the heat source unit (11) to control a required minimum capacity, thereby making it possible to improve COP and extend the range of controllable operations.
Further, if it is arranged such that the target value control characteristic described above can be manually set, an air conditioning capacity to meet the comfortability of a resident can be exhibited. This certainly improves comfortability.
Furthermore, if it is arranged such that the target value control characteristic described above can be learned, then a corresponding air conditioning capacity to the air conditioning load of a building can be set automatically. This provides further improvements in economy and comfortability.